Sir Robert Dillon (died 27 July 1597) was a lawyer, judge and politician in the 16th-century Kingdom of Ireland, and Speaker of the Irish House of Commons.
Dillon was of Newtown, County Meath. In 1545 he was appointed King Henry VIII's Attorney-General for Ireland, under Queen Mary he became second Justice of the Court of Queen's Bench (Ireland), and under Queen Elizabeth he was Chief Justice of the Common Pleas and Speaker of the Irish House of Commons. He was appointed as Chief Justice on 3 September 1559, just before Elizabeth's accession.
William Nugent made complaints that Dillon had abused his position to prosecute members of the Nugent family, and in the summer of 1591 Nugent formally accused Dillon of maladministration of justice. The case was strong: in particular the charge that Dillon had wrongfully condemned William's uncle Nicholas Nugent, his predecessor as Chief Justice, to death for treason.
In the view of Roger Wilbraham, the Solicitor General for Ireland, there was little doubt that Dillon had been guilty of crimes dishonourable to a judge, but Wilbraham considered that
It was no policy that such against whom he had done service for her Majesty should be countenanced to wrest anything hardly against him unless it was capital.
Dillon was suspended as a judge and commissioners were appointed to try the charges, but obstacles were constantly arising, and in November 1593 Dillon was pronounced innocent on all charges and reinstated. On 23 September 1594, the day of his successor's death, Fenton wrote to Burghley that Dillon was to be restored to the chief-justiceship, and this decision was confirmed by patent of 15 March 1594-5, which he retained until his death on 15 July 1597.